In the field of manufacture of a semiconductor device or the like, a shower head for supplying a gas toward a substrate such as a semiconductor wafer in a shower pattern has been conventionally used. To be specific, in a plasma processing apparatus that performs a plasma etching process on a substrate such as a semiconductor wafer, a mounting table for mounting the substrate thereon is installed in a processing chamber, and the shower head is installed so as to face the mounting table. The shower head is provided with a multiple number of gas discharge holes on its surface facing the mounting table, and a gas is supplied toward the substrate through the gas discharge holes in a shower pattern.
In such a plasma processing apparatus, there is known a technology for controlling plasma in a processing space by forming a magnetic field in the processing space by magnets installed around the processing chamber (see, for example, Patent Document 1). Further, there is also known a technology for confining plasma in a processing space by forming a magnetic field in a gas exhaust region of a processing chamber by magnets so as to allow a gas to pass the gas exhaust region and prevent plasma from passing the gas exhaust region (see, for example, Patent Document 2).    Patent Document 1: Japanese Patent Laid-open Publication No. 2003-86580    Patent Document 2: Published Japanese Translation of PCT Patent Application No. 2003-514386
As stated above, in the conventional plasma processing apparatus, plasma is controlled or confined by the magnetic field formed in the processing space. In such a plasma processing apparatus, however, processing rate at a center and a periphery of a substrate such as a semiconductor wafer may become different, resulting in deterioration of uniformity of a plasma process in the substrate surface.